Vibratory deflocculator for papermaking apparatus

ABSTRACT

A VIBRATORY DEFLUCCULATOR FOR BREAKING UP AGGLOMERATES OF FIBERS IN A PAPER STOCK SUSPENSION, AND WHICH ELIMINATES STAPLING. THE DEFLOCCULATOR IS SUSPENDED IN THE STOCK IN, FOR EXAMPLE, THE HEADBOX OF THE PAPERMAKING APPARATUS; IT CONSISTS OF A PAIR OF PERFORATED PLATES SPACED APART BY BAFFLES AND DISPOSED IN PLANES WHICH INTERSECT AT AN ANGLE TO THE PERPENDICULAR. THE PLATES ARE SUSPENDED FROM A SUPPORT BAR BY SPRINGS AND ARE VIBRATED TRANSFERSE TO THE DIRECTION OF STOCK FLOW TO RAPIDLY PUMP STOCK IN ALTERNATE DIRECTIONS THROUGH THE PERFORATIONS.

K. n oPAs 3,562,108

VIBRATORY DEFLOCCULATOR FOR PAPERMAKING APPARATUS Feb. 9, 1971 Filed Jan. 22, 1968 INVENTOR. swmu' Tapas United States Patent O 3,562,108 VIBRATORY DEFLOCCULATOR FOR PAPERMAKING APPARATUS Kasimir Lopas, 118 Skyview Drive, Stamford, Conn. 06902 Filed Jan. 22, 1968, Ser. No. 699,551 Int. Cl. D21f 1/06' U.S. Cl. 162-341 9 Claims ABSTRACT OF THE DISCLOSURE A vibratory deliocculator for breaking up agglomerates of fibers in a paper stock suspension, and which elimin-ates stapling. The deflocculator is suspended in the stock in, for example, the headbox `of the papermaking apparat-us; it consists of a pair of perforated plates spaced a-part by bafiies and disposed in planes which intersect at an angle to the perpendicular. The plates are suspended from a support bar by springs and are vibrated transverse to the direction of stock fio-w to rapidly pump stock in alternate directions through the perforations.

BACKGROUND OF THE INVENTION In the manufacture of paper from fibrous stock, the stock in the form of a liquid suspension is passed through a chamber known as a headbox prior to being ejected as a sheet of liquid onto a moving screen (Fourdrinier wire) :where it is dried. A principal function of the headbox is to distribute fibrous stock evenly across the machine and distribute it onto the wire with fibers being uniformly dispersed in the liquid.

To reduce transverse stock iiow variations in the headbox resulting from localized kinetic energy `variations of the stock entering the headbox, the stock iiow in the headbox is greatly decelerated. -Due to the deceleration and the presence of these iiow variations, large eddy currents are produced in the headbox, causing fiber occulation.

Rectifier rolls, which are hollow perforated rolls, are positioned across the stock fiow in the headbox. They are -used to reduce iiow variations by inducing uniform throttling across the machine and the deiiocculate the stock. These prior art rectifier rolls, however, have produced 'a fiocculation problem of their own. Fibers tend to become entrapped on a hole edge (scooping) or on the land portions between holes on the roll when the fiber ends become caught in adjacent holes (stapling). As a result of these so-called stapling or scooping effects, clumps of fibers are carried by the rotating roll and are fwashed off by the fio-w of stock tangent thereto. These fibrous clumps are then passed out through the nozzle or slice of the headbox to the forming screen where they become incorporated in the paper sheet and degr-ade paper quality.

Rectifier rolls -with large holes produce large flockproducing eddy currents. In rolls having smaller holes and substantial open area, fibers become entrapped on the land portions between holes on the roll to create the stapling effect despite rotation of the rolls.

Ideally, -a deiiocculating device should have considerable open area and have small perforations to produce small eddies or micro-turbulence to avoid stapling.

Accordingly, representative objects of the present invention are to provide an apparatus for deflocculating headboxes without stapling or scooping by means of vibration, and which is simple in construction, efiicient, and reliable in operation.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of Patented Feb. 9, 1971 construction, combinations of elements, and arrangement of parts which Iwill be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

SUMMARY OF THE INVENTION The present invention relates to an apparatus for defiocculating fibrous paper stock, and more particularly to a vibrating defiocculator for use in papermaking apparatus and in particular in the headbox of such apparatus.

Referring to FIG. 1 there is shown a representative configuration for a headbox in papermaking apparatus. In operation, a paper stock suspension is fed from the manifold 10 through a flow distributor 12 and into an explosion chamber 14. From chamber 14 it is fed upward through venturi 16 into headbox 18. Headbox 18 comprises a closed chamber 20 through which the paper stock iiows as shown by the arrows in FIG. l, toward a tapered nozzle with an elongated opening known in the art as a slice 22. From slice 22, the stock is ejected as a sheet of liquid onto a moving forming wire 24 carried on a breast roll 26. The stock carried by forming wire 24 is then dried and processed in subsequent operations to form paper sheet.

It is within the headbox enclosure 20 that the heretofore mentioned problem of stapling has occurred in prior art papermaking apparatus. According to the invention, stapling is eliminated by means of a vibrating defiocculator 25 mounted in headbox enclosure 20 transverse to the iiow of stock.

Defiocculator 25 preferably comprises a pair of perforated plates 28 and 30 (FIG. 2) suspended in enclosure 20 with the faces thereof transverse to the fiow of stock, and aligned in planes intersecting at an angle to the perpendicular. A single plate such as 28 or 30 positioned perpendicular or at an angle to the fiow may also be used. Plates 28 and 30 are caused to vibrate transversely to the flow of stock as it passes through the perforations thereof and thus act to agitate the stock suspension and defiocculate or break up the clumps of fibers which agglomerate therein. In addition, the vibratory motion of plates 28 and 30 causes the stock suspension to be pumped back and forth through the perforations therein; this pumping action quickly dislodges fibers which become caught between perforations and prevents the fiber buildup which has heretofore caused stapling and resultant poor quality paper. Defiocculator 25 also acts to throttle fiow uniformly across the headboX or even-out the velocity of fiow of the stock through headbox 18 so that a more uniform stream issues from slice 22 for improved paper quality.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

FIG. 1 is a side elevation view of a representative headboX for a papermaking apparatus, drawn partly in section to show the positioning therein of the defiocculator of the invention.

FIG. 2 is an enlarged perspective view of the deocculator of the invention.

FIG. 3 is a greatly enlarged partial sectional view through a plate of the deiiocculator, showing one configuration for the perforations therein.

FIG. 4 is a greatly enlarged partial sectional view through a plate of the deflocculator, showing an alternate configuration for the perforations therein.

Similar reference characters refer to similar parts throughout the several views of the drawing.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 2, perforated plates 28 and 30 are suspended within headbox 18 from a rigid, high inertia support bar 32 which is secured to the side walls of enclosure 20 as shown in FIG. 1. Rails 34 between which bar 32 can be mounted may be provided along the length of the side walls of enclosure 20. In this manner bar 32 can slide to vary the position of the deflocculator 2.5 to adjust for different conditions of stock flow and consistency. Bar 32 is secured in position by removable stops or other suitable means.

A flexible suspension for plates 28 and 30 which enhances the vibratory characteristics thereof is provided through pairs of leaf springs 36 and 38, each secured respectively to opposite surfaces of bar 32 and projecting laterally therefrom. A suspension rod 40, 42 is mounted vertically at the free end of each pair of leaf springs 36 and 38 in bushings 44 extending through each spring. The lower ends 40a and 42a of rods 40 and 42 are secured to bailles 46 and 48 which join plates 28 and 30 in their desired angular relationship.

The angular relationship between plates 28 and 30 is determined by the slope of the lateral edges of ballles 46 and 48 as shown in FIG. 2, and plates 28 and 30 are secured to those lateral edges in a suitable manner such as by welding. Preferably, plates 28 and 30 are aligned in planes which intersect at an angle to the perpendicular, and the angles of intersection are identical; for best results the angles of intersection will be from to about 30, depending upon the type of paper stock and the rate of flow through headbox 18.

Plates 28 and 30 are each provided with a large number of perforations 50 which permit the llow of paper stock through the deflocculator 25, and which produce the pumping action which causes deilocculation when unit 25 is vibrated in the manner described below. Perforations S0 may be of any size and shape which will produce the desired pumping action; however, they will preferably be formed as elongated elliptic openings as shown in FIG. 2 to provide maximum open area in the plates 28 and 30. For most papermaking purposes a perforation size of, or corresponding to a circular opening of a diameter, between about %2 inch and 3% inch will be satisfactory.

Perforations 50 may be formed perpendicular to the face of each plate 28 and 30 as shown in FIG. 3. It can be seen with reference to FIG. 3 that by reason of the plate being at an angle to the flow of paper stock (shown by the arrows) the axis of the perforations 50 are also at an angle to the flow. Thus, when the plate is caused to vibrate transverse to the flow, the paper stock is rapidly forced or pumped through the perforations in alternating directions. It is this pumping action which deilocculates the paper stock, and which dislodges any paper fibers which become lodged between the perforations 50 to prevent stapling and its degrading effect on the finished paper product. As shown in FIG. 4, the effective force of the pumping action can be further increased by forming the perforations 50 at an angle to the faces of plates 28 and 30. The perforations 50 may be formed straight or at an angle as shown in FIGS. 3 and 4, and one or more of the plates can also be aligned perpendicularly in headbox 18 rather than at an angle thus preventing stapling due to high frequency vibration with or without a pumping effect. Each of plates 28 and 30 may be provided with one or with combinations of various types of perforations including those illustrated in FIGS. 3 and 4.

The means for vibrating deflocculator 2S is shown in FIG. 2. A vibrator 52, which may be an electrically actuated device of current commercial availability, is secured to support bar 32 and projects laterally therefrom over plates 28 and 30. A vibratory arm v54 projecting downwardly from vibrator 52 connects to a bridging member 56 which serves to transmit vibratory motion over the length of plates 28 and 30. The ends 56a and 56h of member 56 are respectively secured to suspension rods 40 and 42 and thereby transmit vibratory motion through bailles 46 and 48 to the ends of plates 28 and 30. The center of member 56 is connected through bracket 58 to a central baille 60 to transmit vibratory motionv to the center of plates 28 and 30. Batlle 60, like bailles 46 and 48, may be secured to plates 28 and 30 by welding or other suitable means.

In order to obtain the desired deflocculation of the paper stock within headbox 18 (FIG. 1) and to eliminate stapling, the vibratory motion of plates 28 and 30 should have at least one component which is transverse to the flow of paper stock. Accordingly, vibrations may be induced parallel to the width or to the length of plates 28 and 30, or both types of vibrations may be induced simultaneously. In addition, vibrations of a ditfering frequency may be induced concurrently so that phase differences will produce complex vibratory motions if desirable.

It has been determined that to maintain sheet weight uniformity the minimum frequency of vibration should be correlated with the type of papermaking machine and its speed in terms of feet of paper produced per minute. Thus, in open table machines the vibration frequency should be at least equal to the machine speed; for example, in a machine running at 1800 feet per minute the plates 28 and 30 should be vibrated at a frequency of at least 30 cycles per second. For twin wire machines, the vibration frequency should be at least twice the machine speed. -Under normal conditions, a frequency of to cycles per second is adequate; however, vibrational frequencies, especially for plates with little or no pumping effect, as high as in the ultrasonic range may be used.

For maximum etliciency in power consumption, the frequency of vibration of the deflocculator 25 should match its resonant frequency. As will be obvious to those skilled in the art, this may be accomplished by mounting a triggering device 53 to the oscillating arm 54 of vibrator 52. Such a vibrating device may employ a silicon controlled rectifier and will sense the resonant vibrations of plates 28 and 30 through changes in inductance, capacitance or resistance transmitted by the triggering device 53.

While for purposes of illustrating the invention only one deflocculator has been shown in headbox 18, it will be understood that two or more deflocculators may be used where necessary. In addition, the deflocculator may be placed in other portions of the papermaking apparatus where deflocculation and/or throttling may be advantageous.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are eiliciently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover al1 of the generic and specific features of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination papermaking apparatus, a vibratory deflocculator for fibrous paper stock comprising:

(A) atleast one plate:

(1) mounted in a ilowbox with a face transverse to the flow of stock through said lowbox,

(B) a plurality of perforations through said face of said plate, the axes of said perforations being disposed at an angle to the direction of ilow of said stock and at an angle to the bottom of said flowbox,

5 (C) vibrating means causing said plate to vibrate in said stock with at least one component of said vibration transverse to the direction of ow of said stock, whereby said stock is pumped through said perforations to prevent fiber stapling.

2. A deocculator as deiined in claim 1 comprising two plates mounted in opposed relation in said apparatus with opposing faces thereof being separated, said two plates both being Vibrated by said vibrating means.

3. A deflocculator as dened in claim 2 wherein said plates are mounted in intersecting planes each making an identical angle of up to about 30 with a plane perpendicular to the direction of flow of said stock.

4. A deocculator as defined in claim 1 wherein there is provided triggering means for said vibrating means to vibrate said plate at its resonant frequency.

5. A deocculator as dened in claim 1 wherein said plate is spring mounted to enhance the vibration thereof.

6. A deocculator as deined in claim 1 wherein said perforations correspond to a circular diameter of from about 3/32 of an inch to 3/4 of an inch.

7. In a headbox, a vibratory deocculator comprising, in'combination:

(A) a pair of opposed plates:

(1) mounted in said headbox transverse to the direction of flow of stock therethrough and (2) secured together in spaced relation,

(B) a plurality of perforations through the face of each said plate,

(1) the axes of said perforations being disposed at an angle to the direction of said stock ow,

(C) spring means suspending said plates in said headbox for vertical movement, and

(D) vibrating means causing said plates to vibrate in said stock with at least one component of said vibration transverse to the direction of ow of said stock.

8. A deocculator as defined in claim 7 wherein said plates are aligned in intersecting planes each of which is at an angle to a plane perpendicular to said stock flow.

9. A deocculator as defined in claim `8 wherein said perforations traverse the thickness of their respective plates on an incline.

References Cited UNITED STATES PATENTS 9/1963 Justus 162-341 6/1967 Bennett 162-341 U.S. lCl. X.R. 162-343 

